Ethylenediaminetriacetic acid (ED3A) or its salts (such as ED3ANa.sub.3) has applications in the field of chelating chemistry, and may be used as a starting material in the preparation of strong chelating polymers, oil soluble chelants, surfactants and others. Conventional routes for the synthesis of ethylenediaminetriacetic acid were achieved via its N-benzyl derivative, which was subsequently hydrolyzed in alkaline solutions to ED3ANa.sub.3, thus avoiding cyclization to its 2-oxo-1,4-piperazinediacetic acid (3KP) derivative. Syntheses attempted by both the alkaline condensation of chloroacetic acid with ethylenediamine, and the carboxymethylation of the diamine with formaldehyde and sodium cyanide resulted in complex mixtures requiring complex extraction techniques (e.g. almost exclusive solubility of 3KP in boiling dimethylformamide, Can. J. Chemistry 1970, 48(1), 163-175) to generate the desired product, and then in only relatively poor yield. In addition, conventional processes resulted in large quantities of by-product, such as ethylenediaminetetraacetic acid (ED4A). Where the by-products were especially objectionable, complicated blocking techniques were necessary in order to achieve a relatively pure solution.
One example of the synthesis of ethylenediamine-N,N,N'-triacetic acid is shown in Chemical Abstracts 78, Vol. 71, page 451, no. 18369c, 1969. There it is disclosed that ethylenediamine reacts with ClH.sub.2 CCO.sub.2 H in a 1:3 molar ratio in basic solution at 10.degree. C. for 24 hours to form a mixture from which ethylenediamine-N,N,N'-triacetic acid can be separated by complexing the same with Co(III). The resulting cobalt complexes can be isolated through ion exchange.
It is therefore desirable to produce ethylenediaminetriacetic acid or its salts in high conversions and excellent yield.